ISSN:1040-5488    

出版商:OVID    

年代:2001

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2001

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2001

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2001

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2001

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

BackgroundSuperior epithelial arcuate lesions (SEALs) are an infrequent and often asymptomatic complication of conventional soft contact lens wear. The characteristic arcuate pattern of the full-thickness corneal epithelial lesion usually occurs in the area covered by the upper eyelid, within 2 to 3 mm of the superior limbus in the 10- and 2-o’clock region.MethodsLiterature on SEALs and recent clinical records from clinical trials using two types of prototype high Dk soft contact lenses were reviewed to gain greater insights into the etiology of SEALs.Results and ConclusionsThe reported low incidence of SEALs is partly because SEALs are not usually symptomatic. The etiology of SEALs is multifactorial. Our current hypothesis is that SEALs are produced by mechanical chaffing at the peripheral cornea. This chaffing occurs as a result of inward pressure of the upper lid, in an area where the peripheral corneal topography and lens design, rigidity, and surface characteristics combine to create excessive “frictional” pressure and abrasive shear force on the epithelial surface. Patient characteristics such as gender, age, and specific corneal and lid topographies also appear to influence the occurrence of SEALs. Prototype silicone hydrogel lenses are made from higher modulus materials with surfaces that seem to differ subtly in wettability in some patients. The prevalence of SEALs may well increase with the first generations of these lenses.

ISSN:1040-5488    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

PurposeTo categorize the appearance of the normal upper palpebral conjunctiva using a grading scale and to investigate interobserver agreement with a grading scale modified to include decimal increments.MethodsUpper palpebral conjunctival appearance of 96 non-contact lens wearing subjects aged 18 to 75 years was assessed using a photographic grading scale that has a generic (zero to four) scale to score redness and roughness of the palpebral conjunctiva.ResultsMedian redness and roughness was about 1.25 units. About 5% of subjects had redness or roughness >2.0 units. Interobserver agreement improved during the study. By the end of the study, the standard deviation of the discrepancy scores was 0.12 to 0.19 units.ConclusionsUpper palpebral conjunctival redness or roughness >2.0 units are unusual. The grading scale can be used successfully with decimal rather than integer scale increments. For experienced clinicians, a change in grade of ≥0.5 units may be significant.

ISSN:1040-5488    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

BackgroundInternational Organization for Standardization (ISO) document ISO 9913-1 details procedures for oxygen permeability coefficient (Dk) measurement of hydrogel contact lens materials up to 100 barrer. A draft ISO document 9913-2 describing the coulometric technique states that the recommended procedures are suitable for nonhydrogel materials. New generation hydrogel lens materials exceed 100 barrer, which is outside the scope of both documents.MethodsA range of rigid gas-permeable materials from Dr. W. Benjamin’s standard repository was used as a baseline to assess the accuracy of the polarographic and the coulometric methods. We also measured the permeability of a new generation hydrogel, lotrafilcon A, to explore the suitability of the polarographic and coulometric techniques for high-Dk hydrogel lenses. We modified equipment for both methods that incorporate several improvements including front surface masking to eliminate “edge effect.”ResultsThe coulometric technique provided results similar to those previously reported for the standard rigid gas-permeable materials and yielded relative standard errors typically <10%. The polarographic technique provided results similar to the accepted values for the standard rigid gas-permeable materials Dk <70 barreronlyafter the edge effect correction algorithm was applied. The polarographic results showed poor precision and significant, systematic differences from accepted values for the rigid gas-permeables with Dk >70 barrer.ConclusionsThe coulometric method is preferable for the measurement of contact lens materials with permeability >70 barrer. The coulometric method was successfully modified to include hydrogels.

ISSN:1040-5488    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

PurposeScanning fluorophotometry is considered the “gold standard” to determine tear turnover rates (TTR). In this study, we attempted to improve the precision of basal TTR by fluorophotometry through a number of methodological changes.MethodsBy means of a timer program that produces audio cues, a new methodology that ensures confluence and a constant thickness of the tear film and minimization of reflex lacrimation as a result of the inhibition of the blink reflex was developed. This was compared with the standard protocol, both in a paired study and by a review of unpaired data. The minimum length of time required to monitor TTR measurements was also investigated.ResultsA significant improvement in correlation coefficient (r) of the log decay curve was observed as a result of changes in the protocol in both the paired (p = 0.016) and unpaired study (p < 0.0001). We determined that it was sufficient to monitor TTR for 10 min to obtain accurate results.ConclusionsWe advocate that the changes be adopted as widely as possible for the precise and rapid measurement of basal tear turnover rates.

ISSN:1040-5488    

出版商:OVID    

年代:2001

数据来源: OVID